The chief federal judge of Montana has apologized to President Barack Obama in a letter after admitting to sending an email containing a racist joke about the president that made a reference to a dog.

“I sincerely and profusely apologize to you and your family for the email I forwarded. I accept full responsibility; I have no one to blame but myself,” Chief U.S. District Judge Richard Cebull wrote in a letter dated March 1. “I can assure you that such action on my part will never happen again.”

He added, “Honestly, I don’t know what else I can do. Please forgive me and, again, my most sincere apology.”

“A little boy said to his mother; ‘Mommy, how come I’m black and you’re white?’” the joke in the email said. “His mother replied, ‘Don’t even go there Barack! From what I can remember about that party, you’re lucky you don’t bark!’”

In a note preceding the joke, Cebull had written, “Normally I don’t send or forward a lot of these, but even by my standards, it was a bit touching. I want all of my friends to feel what I felt when I read this. Hope it touches your heart like it did mine.”

The incident made national headlines and drew the ire of some members of Congress, including the heads of the Congressional Black Caucus, Congressional Hispanic Caucus and the Congressional Asian Pacific American Caucus, who came together to issue a joint-release condemning the judge.

Rep. Charles Gonzalez (D-Texas), the chair of the CHC, told POLITICO Thursday that Cebull must resign from the bench.

In addition to writing to the president, Cebull also penned a letter to Chief Judge of the Ninth Circuit Court of Appeals Alex Kozinski, which requested a self-initiated investigation into his own “misconduct.”

“I have apologized publicly and profusely for my serious mistake and lack of judgment, and have today written a personal letter of apology to the President of the United States, a copy of which is attached,” Cebull wrote to Kozinski. “I waive any confidentiality as to making this request or to the existence of any proceedings that may ensue from it.”

The Ninth Circuit consequently stated that its judicial council will “act expeditiously” in probing and resolving the matter.